Process of preparing an explosive



Patented Jan. 20, 1948 2,434,8'l9 raocEss or PREPARING AN EXPLOSIVEYGeorge F. Wright, Henry H. Richmond, and Douglas 0. Downing, Toronto,Ontario, Canada, assignors to The Honorary Advisory Council forScientific and Industrial Research, Ottawa, Ontario, Canada, acorporation of Canada No Drawing. Application July 16,1943, Serial No.495,082

4 Claims. (Cl. 260-248) 1 The present invention relates to'a highexplosive known as cyclonite and moreparticularly to a new and improvedmethod of producing the same.

Cyclonite is an explosive of great power and brisance obtainable by thedirect nitration (nitrolysis) of hexamethylene tetramine (hexamine) withconcentrated nitric acid at about to 40 C. Within recent times animproved. method of preparing cyclonite was proposed by W. E. Bachmannin application Serial No. 495,078, filed July 16, 1943. According to theBachmann procedure in one of its preferred embodiments, hexamine istreated at a reaction temperature above about 35 to 40 C. (Preferably at60 to 90 C.) with an ammonia donor (e. g., ammonium nitrate) andconcentrated nitric acid in the presence of a fatty acid anhydride-suchas acetic anhydride, according to the overall equation 1)Hexamine+4HNOs+2NH4N03+6AczO= 2 cyclonite+12AcOH The reactants may beused in about the proportions indicated by Equation 1, but preferablywith an excess of the nitric acid, ammonium nitrate and anhydride.

The process indicated by the overall Equation 1 involves the use of twosolids (hexamine and ammonium nitrate) and two liquids (nitric acid andacetic anhydride. In order to obtain optimum yields of cyclonite by thisprocess, the proportions of the reactants should be very carefullycontrolled to maintain the proper ratios throughout the course of thereaction. For this reason, portion-wise addition of the reactants to thereaction vessel is essential for optimum yields. Thus, in one of themodifications described in the above identified Bachmann application,the solids are introduced in approximately 100 separate, substantiallyequal portions.

It will be apparent that the foregoing procedure does not lend itselfreadily to large scale manufacture. It is therefore one of the objects Iof the present invention to provide a commercially more feasible andexpeditious method of carrying out the Bachmann process of producingcyclonite.

Another object is the provision of a method whereby proportionatequantities of the reactants (hexamine, nitric acid, ammonium nitrate andacetic anhydride) may be fed to the reactor in the form of liquids,thereby obviating the disadvantages arising from the use of one or moresolid feeds.

Afurther object is to provide a modification of the Bachmann procedurefor the production of cylonite, which lends itself to large scalemanufacture.

Other objects and advantages will be apparent as the invention ishereinafter more particularly described.

, We have found that the foregoing objects may be accomplished bycombining two of. the reactants to form a solution and by dissolvinganother of the reactants in a suitable solvent. More particularly, theimprovement of the present invention involves the followingmodifications of the Bachmann procedure:

(1) Dissolving the ammonium nitrate required in the reaction, in thenitric acid, to form a solution which (after the evolution of a smallamount of gas), ultimately becomes a clear liquid; p

(2) Dissolving the hexamine in a convenient amount of a substantiallyanhydrous liquid fatty acid such as glacial acetic acid or propionicacid;

(3) And then bringing (a) the clear ammonium nitrate-nitric acidsolution, (1)) the hexamine-fatty acid solution and (c) the liquid fattyacid anhydride used in the process, into reactive relation underconditions suitable for the production of cyclonite.

It will be apparent that in the aboveprocess all of reactants charged tothe reaction vessel are in the form of liquids, thereby obviating allthe mechanical difficulties associated with the portionwise additionof'one or more solid feeds. In general, the reaction may be carried outunder the conditions and with the proportions of reactants indicatedabove, it being understood, of course, that a sufficient amount ofnitric acid and liquid fatty acid are used to dissolve all the ammoniumnitrate and hexamine, respectively.

As previously indicated, the ammonium nitrate-nitric acid solution, wheninitially formed, evolves a small amount of gas which appears to be theoxides of nitrogen contained in the concentrated nitric acid. At anyrate, the solution becomes clear if permitted to stand for a time, sothat the nitric acid is in effect, purged of its yellowish color. Theresulting clear solution may be used immediately, or stored (above 28C.) for future use, with or without prewarming (from 28 C.) to theselected reaction temperature before being charged to the reactionvessel. The hexamine-glacial acetic acid solution also appears to bequite stable and may be used in a the present invention, a preferredembodiment will now .be described in detail. It .should besunderstood,however, that this is done solely by way of example, and is not to beconstrued as a limitation upon the spirit and scope of the appendedclaims.

Example 1.7 moles of acetic anhydride "was placed in -'a 1-liter3-necked flask equipped with stirrer, thermometer, and suitable meansfor the introduction of two solutions from buret'tes. The flask wasplaced in a water bath iconld'zhe heated by steam, cooled with tap water101' drained. To begin the reaction, the bath was heated to about 20 0.below the selected addition temperature (e. g., 60-,80 .C.) for theprewarmed reactants.

The two prewarmed solutions, one containing .48 mole ammonium nitrate in1.11 moles of 9.7% nitric acid, the other, :24 nrole of hexamine in 160cc. of glacial acetic acid, were introduced from the burettes in 30alternate substantially stoic'hiometric proportions. The reactiontemperature '(50-9U -(3., preferably 60 to 65 C.) was maintained at theselected point by suitable regulation of the bath temperature and therates ofaddition,

After the reactants had all been added, the reaction mixture was stirredfor a period of time (I) .to 60 minutes, preferably 15 to 20 minutes) atthe selected reaction temperature and then diluted with v6 95i cc. ofhot water, .after which the reaction mixture was allowed to stand at 25C. for four hours or more, then filtered and the precipitate washedwith water. The crude yields ranged from about 75% to about 85% of thetheoretical, based on overall Equation 1 above, the melting point of.the crude cyclonite varying from about 160 to 196 12,, depending on thereaction conditions.

The crude cyclonite was purified by dissolving the .cyclonite in boiling50%, 150% or 70% nitric acid until the evolution of brown "fumes ceasedand the boiling liquid was coloredpale yellow or yellow-orange. In mostcases, boiling for 5 to minutes was required. The clear solution wasthen diluted With an equal volumeof water, and after cooling, the solidwas filtered, washed with water and dried to constant weight at 70 .C.This treatment raised the melting point to around 2il0 C.

One of the indirect advantages of theprocess of the present inventionarises from the fact that a nitric acid solution of ammonium nitrate ismuch less rapidly corrosive to the flesh than concentrated nitric aciditself. Thus the solution, if promptly flushed with water from theflesh, does not produce the characteristic yellow coloration and painfulburn caused by 98% nitric acid.

It may ?be mentioned {that certain changes in the foregoing proceduregive results which are far less satisfactory. Thus if the hexamine isdis- .solved in the acetic anhydride (instead of using .glacial aceticacid). the yield is definitely inferior (for example, 18%) .It will beapparent that the foregoing procedure lends itself :a'dmirably to theproduction of cyclonite in the apparatus described and claimed in thedepending application of David C. Hull, Ser'iaTNo. 495,083,1iled July 3,1944. Other variations and applications of the present invention will beapparent to those skilled in the art. We therefore intend to be limitedonly in accordance Withthe following patent claims.

We claim:

.1. honethod of producing cyclonite'which loomiprises forming=a:solution of-ammonium nitrate in nitric acid and a solution of'hexamine substantially anhydrous liquid fatty acid, feeding saidsolutions in alternate portions into liquid fatty "acid anhydride, andmaintaining the reaction temperature between 50 and C.

A method of producing cyelonite which comprises forming a solution ofammonium nitrate in nitric acid and a solution of hexamine in -gla cialacetic acid, feeding said solutions in substantially s'toichiemetricproportions in alternate portions into acetic anhydride and maintainingthe reaction temperature at about 60-65 3. a method as defined in claim1 wherein said solutions and said acid anhydride are prewarmed toreaction temperature before being brought into reactive relation.

4. A method as defined in claim 1 wherein said solution of ammoniumnitrate in nitric acid is allowed to stand until the evolution of gastherefrom ceases before .feeding it into the .acid -an "hydride.

GEORGE F. WRIGHT.

DOUGLAS (3. DOWNING.

REFERENCES CITEB The following references are of record in the file ofpatent:

Name

GTHER REFERENCES Tanner, Chemical and Me'tallurgi cal Engineering, vol.29, No. 10, page 404.

